1. Field of the Invention
The present invention relates to a method of managing backup of data, and particularly relates to a technique for efficiently performing management of generation of backed-up data in a case where storage devices are operated according a mirroring method.
2. Description of the Related Art
There exist various mechanisms in the art relating to methods for managing backup of data stored in a storage system such as a disk array device. For example, in Japanese Patent Application Laid-open Publication No. 2001-159993, there is disclosed a mechanism for restoring a database to a state at an arbitrary point of time in the past by, upon updating a database, storing data before update in a section for accumulating history, and managing information before update by taking an update time as a key. Further, in Japanese Patent Application Laid-open Publication No. 2001-125815, there is disclosed a method wherein, when an updating process is executed by a host device in view of a storage subsystem, a log containing a data-write time, a location at which data is stored, and data contents is obtained, and restoration of data is performed according to this log. Further, in Japanese Patent Application Laid-open Publication No. 8-185346, there is disclosed a data copying method wherein: a device to be backed up (a “to-be-backed-up device”) and a device used for backup (a “backup device”) are connected via a network; a table for managing update history (an “update-history management table”) is provided in the to-be-backed-up device; and with reference to the update-history management table, data in the to-be-backed-up device is copied to the backup device in a delayed manner by transmitting data in the to-be-backed-up device to the backup device in time series across a communication line.
Upon data restoration, it is ideal to restore data to a state as close as possible to that right before occurrence of trouble, in order to minimize time and/or effort for performing re-inputting and re-updating of data. Therefore, in managing data backup, it is essential to provide a mechanism for managing the generation of the backed-up data. However, in order to perform generation management, it is necessary to provide, for example, a mechanism for periodically performing backup and/or a mechanism for accumulating and recording a data-update log; this tends to lead to system complication and increase in operation load.
Meanwhile, in recent storage systems such as disk array devices, there are many cases where a method so-called mirroring (or RAID 1) is applied. Here, the same data is synchronously managed among the two storage devices X, Y which structure a mirrored pair, and the storage devices X, Y are in a relationship where the units mutually back up the data stored respectively in each of the units.
The present inventors have conceived a backup-management method capable of efficiently performing generation management by applying such a mirroring mechanism.